Oilpan: Remove a FIXME in Visitor's eager tracing
Oilpan: Remove a FIXME in Visitor's eager tracing

The FIXME was added in https://codereview.chromium.org/818253005/
but we've already removed the hack from traceInCollection and the issue is gone.
I think it's now safe to remove the ASSERT(... || isMarked(t)).

BUG=474458

Review URL: https://codereview.chromium.org/1070513002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@193754 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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